Spy Hunters Find Clews in Secret Codes (Jun, 1938)

WORKING swiftly, Federal agents a few-weeks ago spread a tight dragnet over New York City. In a midtown hotel, they nabbed a former U. S. Army sergeant. At a near-by Air Corps base, they detained a foreign-born private in the Army aviation service. And as a large transatlantic liner nosed into her dock, a few days later, two secret operatives emerged from the shadows of the pier to arrest a woman attendant in the ship’s beauty shop.

Next morning, the Federal Bureau of Investigation revealed that with the capture of the two men and their attractive confederate, they had smashed a particularly dangerous ring of international spies.

The men were accused of relaying stolen military information to an unnamed foreign power through secret code messages carried abroad by the beauty-shop operator. Rumors hinted that their booty included the secret code of the Army Air Corps.
Such a prize would richly reward the most risky stratagems of a potential military enemy’s secret agents. For codes, the most sought-after and closely guarded of military secrets, provide the key to the secret communications of the nation’s fighting forces.

While counter-espionage agents match move for move with code thieves, cryptographers here and in every other major country are striving to develop new kinds of war codesâ€”complicated methods for writing secret messages that will defy solution unless the well-guarded key is known, codes that can be used safely by spies as well as by army and navy officials.

To this end, ingenious automatic coding and decoding machines have been perfected. In one such device, a code clerk simply types off the message as he would on a typewriter. As he does so, an intricate mechanism cuts a series of notches and perforations into a moving strip of paper tape. Only a duplicate machine, it is said, can decipher the communication.

Another coding machine, details of which have just been revealed, makes use of the principle of the modern facsimile apparatus that transmits pictures hundreds of miles in a few minutes. In the standard commercial apparatus, an electric eye scans a revolving cylinder bearing the picture to be transmitted, and converts its high lights and shadows into electrical impulses. When these impulses reach the receiving station, the process is reversed, and they actuate a lamp or a stylus that builds up the same high lights and shadows upon a piece of paper attached to a second revolving cylinder. Both the transmitting and receiving cylinders turn at constant speed, and the very essence of successful transmission lies in their perfect synchronism with each other.

In the new code machine, however, just the reverse is true. Like a worn-out phonograph, the cylinder turns at a constantly varying speed. After each revolution it stopsâ€”and after an interval apparently determined by nothing more than sheer aimlessness, it starts again. Try as he will, a wire tapper or listener-in will get nothing but an undecipherable jumble of dots and lines, for no matter

whether he speeds up or slows down a standard receiver it cannot possibly be synchronized with the transmitter.

Where coding machines are not available, however, secret agents still rely on standard modes of ciphering to disguise their reports. There are literally thousands of these cipher methods, but all of them can be broadly divided into two classificationsâ€”substitution and transposition ciphers.

IN THE latter, the letters of a message are transposed out of their regular order, and then unscrambled by the person possessing the key to the cipher. The order “COME AT ONCE,” for instance, might be put into cipher so that it read “ECNO TA EMOC” â€”the message written backwards. It also might be written “CMAOC OETNE.” To decipher the latter, the receiver would place the second word underneath the first, and read down each two-letter column.

A version of this type of cipher was decoded by counter-espionage agents of a foreign power just in time to trap a spy about to deliver drawings of a vital military secret to be smuggled out of the country. The suspected spy was trailed as he entered a pet shop and began studying the tropical fish swimming around in glass tanks on a long display table. When he left, the agents noticed cryptic words written below the printed prices on cards in front of the tanks. Believing that the spy might have read a message in these “meaningless” words, they copied them down and turned them over to code experts. Cryptographers puzzled over the strange conglomeration of letters: “ETSYTIE NENTAWV OEIRSAA TRAOGRE ATMFNDL.”

IN THE nick of time they hit upon the key by setting the jumbled words down, one below the other, and then reading the letters up each column, starting from the lower right-hand corner:

E T S Y T I E
NENTAWV
OEIRSAA
TRAOGRE
ATMFNDL

Needless to say, Government men were on the job at 40 Main Street at one o’clock to trap the spy and recover the drawings.

These transposition ciphers are generally easier to decode than the more complex substitution type in which a different letter is substituted for each letter of the original text. “COME AT ONCE,” for instance, might be written “DPNF BU PODF”â€”the next letter of the alphabet being used for each letter of the message.

To aid them in coding and decoding substitution ciphers quickly, cryptographers often use what is known as a “St. Cyr slide.” This is a simple device that is easy to make from two ruler-size strips of paper or cardboard, one having the alphabet lettered across it, and the other having a double alphabet similarly set down. By placing the letter A marked on the smaller slide below a given letter on the upper slide, it is a simple matter to code or decode messages.

IF THE letter A, for example, is placed below H, the letter S will appear below Z, C below J, and I below P. The word “SCIENCE” will then be written in cipher as “ZJPLUJL.” Move the slide by one letter, so that A is below G, and a new cipher will be in use. “SCIENCE” will then be written “YIOKHIK.”

Although expert cryptographers, trained for years in deciphering codes, seldom fail to ferret out the meaning of the most complicated of these substitution ciphers, an amazing machine that has just been invented may change the picture, for it is said to permit the use of more than 1,000,000 cipher combinations. To work the machine, the operator first adjusts four electrical scrambling disks to a given combination and then strikes the first letter of the message on the unit’s typewriter keyboard.

In a panel adjacent to this keyboard, a small lamp glows to indicate the cipher letter to use in the code message in place of the one just typed on the machine. Each time a letter is typed, the scrambling disks whirl, changing the combination. This means that if the letter E were tapped out twice in succession, the light representing the letter G might go on the first time, and the one representing J the second.

CODES and ciphers have been used since the times of the early Egyptians, and the number of secret communication methods runs to a staggering total. Some are as complex as the Einstein theory and others as simple as a nursery riddle. In variety, they range from complicated cryptograms to perforations in the top of a tin can, an arrangement of pins in a pincushion, stitches of varying length in the seam of an overcoat, and water at different levels in a row of bottles.

One code, used by the Germans during the war, seemed very complex, but turned out to be simple when baffled American cryptographers finally ferreted out the key. The powerful radio transmitter at Nauen, Germany, kept buzzing out messages which consisted of nothing but numbers. 12141, 62635, 09912,10161â€”five-digit numerals poured into the air with no indication of a signature nor an address. Code experts

sweated over the problem day and night, until one of them had a bright idea.

Possibly each number referred to a specific word in a book, the first three digits indicating the page and the next two the line down from the top. This proved to be the case. Each number referred to a specific word in the English section of an English-French dictionary. Once they had established this, decoding was simply a matter of turning in the volume to the page indicated by the first three digits, and selecting the word defined on the line specified by the last two.

AS LONG as both sender and receiver i know what book is being used, this system can be employed with any of the millions of volumes available throughout the world. It could also be used in conjunction with a magazine, by having the first three digits of a number indicate the page, the next one the column; the next two the line, counting from the top; and the last one the specific word, counting in from the left. Headlines and captions would be ignored.

Here, for example, is an interesting physiological fact, transposed into this number code by using the May 1938 issue of Popular Science Monthly:

Another simple code that can be exceptionally baffling permits a person to put a message into cipher as fast as he can bang it out on the typewriter. And anyone knowing the solution to the code can make his own typewriter decipher the message automatically.

The trick here is to buy or make a set of lettered covers for the typewriter keys. These are then placed over the keys so that the cover bearing a given letter covers a different letter on the keyboard. As an example, the letters on the top row of letter keys might be reversed like this:

Standard keys: QWERTYUIOP

Lettered covers: POIUYTREWQ

TYPE out the word “POWER” on the lettered covers and the machine will print the cryptic word “QWOIU.” The person receiving the message places a set of the key covers on his machine in exactly the same order. Then, when he types off the word “QWOIU,” the decoded word “POWER” will appear on the paper.

Each year, cryptographers are devising ever more baffling codes for secret communication, but each new trick soon becomes useless as other experts locate the key that unlocks the secret. Coding machines may provide the solution to the search for an unbreakable code, but as yet, cryptographers agree that their favorite saying is still true â€””What the brain of man can hide, the brain of man can uncover.”